Baculovirus, including Bombyx mori nucleopolyhedrovirus (BmNPV) and Autographa californica nucleopolyhedrovirus (AcNPV), belong to a diverse family of arthropod viruses that are characterized by large (80 to 180 kb) circular double-stranded DNA (ds DNA) genomes and rodshaped enveloped virions. BmNPV and AcNPV are widely employed as vectors for the expression of eukaryotic proteins and pest control (Maeda 1989). To maximize the yield of protein from a baculovirus expression system, optimal infection of the host cell culture must be achieved. In order to obtain such optimal infection, the titer of the virus inoculation must be known (King and Possee 1992; Luckow 1993; O'reilly, Miller, and Luckow 1994). Currently, determining the titer of virus stocks is a major time-consuming step in baculovirus gene expression. The most frequently used methods for the titration of baculovirus stocks are end-point dilution and plaque formation (King and Possee 1992; Luckow 1993; O'reilly, Miller, and Luckow 1994). Both the end-point dilution and plaque formation methods require the seeding of cells onto plates, precise 10-fold dilutions of virus stocks, and measurement of viral infection in 4-7 days post virus infection. These are lengthy procedures that are also difficult to perform for scientists who are not familiar with baculovirus expression vector systems. Later on, many other reporter genes, e.g. β-galactosidase (Sussman 1995; Yahata et al. 2000) or green fluorescent protein (GFP) genes (Chao, Chen, and Li 1996; Cha, Gotoh, and Bentley 1997; Wilson et al. 1997), were used in order to more easily detect viral infections; although these reporters improved the sensitivity of detection, they did not significantly reduce the time and effort needed to obtain a titer. To reduce the time for titer determination, several methods were further developed in recent years. Kitts and Green (1999) developed an immunological assay for the determination of baculovirus titers; this technology can determine the titer of a given virus stock within 48 hours. However, in this procedure, cell seeding, virus dilution and infection is still tedious. In 2002, Knon, Dojima, and Enoch developed an antibody-based assay that detects early viral gene products, DNA-binding protein (DBP), in order to determine the titer of baculoviruses; by the detection of early viral gene products, this method could determine the titer of the virus within 10 hours. However, this antibody-based titration assay using expression of DBP is a laborious process which is not reliable due to the fluctuation of the yield of the DBP expression from one cell to another which may lead to inaccurate titer determination; moreover, the rabbit polyclonal antibodies against the DBP used are not adequate enough to recognize DBP specifically. Recently, Lo and Chao (2004) developed a quantitative real-time polymerase chain reaction (Q-PCR) for titer determination of baculovirus. This method is based on the quantitative amplification of the 150-bp fragments of viral DNA using the Q-PCR technique. However, this procedure is laborious, costly and not suited for any laboratory interested in research related to baculoviruses. Indeed, this Q-PCR technology requires many labor-intensive steps for the extraction of highly pure viral DNA using the commercial column and for the construction of recombinant viruses; in addition, performing the Q-PCR titration assays require the use of the expensive LightCycler instrument that not all laboratories can afford to have. Thus, the current situation of the field shows that there is a need to design an easy, simple, and cost-effective procedure for quantitative titer determination of baculoviruses. To address this issue, the present invention offers a new procedure using an approach different from previous ones. The new procedure involves the DBP gene derived from AcNPV (AcNPV DBP) as a target for the development of a simple, rapid, and universally applicable titration method. This procedure entails the amplification of the AcNPV DBP gene by using the PCR technique in the presence of digoxigenin-11-dUTP and the synthesis of the specific biotin label nucleotide probes directed to the AcNPV DBP gene. These specific probes are then used in the Enzyme Linked Immunosorbent Assay (ELISA) for the quantitative determination of baculovirus titer.